Diesel or compression ignition engines experience various operational difficulties in cold or sub zero temperatures. Hard starting can be a common problem caused by various mechanisms. The hard starting problem exists with mobile engines such as those in large trucks, buses and even smaller trucks such as the 6.0L and 6.4L engines manufactured by FORD® and those of other vehicle manufacturers. Engines for fixed installations often also encounter the similar difficulties in starting in cold weather.
Typical hard starting mechanisms include reduced battery currents at low temperatures, decreasing the electrical power available to start the engine. Improper atomization of fuel in the cylinder makes it harder to mix the fuel with the air to achieve combustion. This is typically caused by the injected fuel failing to atomize, because it is condensing on the cylinder surface. Also at cold temperatures the lubricating oil covering various surfaces tends to thicken to the point that increased resistance to cranking the engine can be experienced, often further taxing a battery that may be operating at a reduced output.
Various systems and devices that may be utilized to improve starting in cold weather can include battery heaters (to produce higher battery output), engine block heaters (to reduce oil viscosity, and reduce fuel condensation), glow plugs (installed in the cylinder to prevent fuel condensation) and the like.
Proper lubrication can also be a problem in cold weather operation. The cold diesel fuel injected into the cold cylinders can condense, and passes along the cylinder walls, diluting the lubricating oil.
In addition to the difficulty of cold starting, lubrication in cold weather operation can also be a problem. The engine lubricating oil becomes more viscous in cold temperatures, reducing its effectiveness in lubricating engine components during startup and initial operation. Some operators elect to use an oil such as an exemplary OW-20 to allow for easier cold weather starting. However, once the engine is warmed, the oil film thickness in bearing surfaces may drop below that recommended by manufacturers. Thus, another problem operators of diesel engines encounter during cold weather operation is to select an oil that will adequately lubricate and will not contribute to starting difficulties.
Since diesel engine's operate in all seasons hot weather operation is a consideration in their design as well. To aid hot weather operation, diesel engines are often equipped with engine oil coolers that tend to reduce oil temperature during hot driving conditions, and to keep the oil at a proper viscosity level (because of its temperature) to properly lubricate the engine. However, engine oil coolers do not aid engine operation in cold environments where it is often desirable to warm the oil, not take heat out of it. If engines having an oil cooler could be fitted with a device to aid cold weather starting and operation then the useful temperature range of a diesel engine and its performance might be improved.
And in cold weather there also exists a need for a lubricating oil system for diesel engines that will enhance starting capability and allow users to select a grade of oil which will provide adequate lubrication.